Fatty acid treatment



what QESQ t Lommol @Stom MNM Dec. 15, 1942.- J. E. MCKEE ETAL FATTY ACIDTREATMENT Filed June 22, 1959 k Sow .AII/Iii..

TLM mmhwmr ummm QN .Ar MUNI Patented Dec. 15, 1942 2,304,342 FATTY AcmTREATMENT John E. McKee, Western Springs, and Orlando Graziani, Chicago,Ill.. assignors to Armour and Company, Chicago, Ill., a corporation ofIllinois Application June 22, 1939, Serial No. 280,594

11 Claims. (Cl. 26o-409) The present invention relates to the treatmentof triglycerides and their fatty acids and has particular reference toan improved Aprocess for increasing the degree of saturation of oils andtheir fatty acids by hydrogenation.

Triglycerides contain both saturated and unsaturated fatty acidradicals. For many uses it is desirabl Lthat the degree of saturation ofthe fatty acids be increased. The common practice for increasing thesaturation of fatty acid radicals is hydrogenation. This procedureinvolves the well known steps of subjecting the fatty acid radicals,usually in the form of triglycerides, to heat and pressure in thepresence of a nickel catalyst. The hydrogenation may be of thetriglycerides or of the hydrolyzed fatty acids. In some cases thehydrogenation proceeds without difficulty and relatively little catalystis necessary for the operation. In other instances, and particularly inthe case of fatty acids, the hydrogenation procedure is effected with,difficulty, a relatively large amount of catalyst being required toproduce an effective reduction of the iodine number of the material. Thepresent invention has for its principal object the effective andeconomical hydrogenation of this latter type of material whichIheretofore has been resistant to treatment. l

A further object of the invention is the provision of an improvedprocess for treating unsaturated triglyceride oils containinghydrogenation inhibiting factors, which includes hydrolyzing the oils toproduce a mixture of volatile fatty acids carrying the hydrogenationinhibiting factors in volatile form, subjecting the fatty acids tofractional distillation, recovering one fatty acid fraction containingthe volatile hydrogenation inhibiting factors, recovering a second fattyacid fraction free from these factors, subjecting the latter fraction tohydrogenation, and reacting the hydrogenated fatty acid fraction withglycerine to produce a synthetic triglyceride or with some differentmaterial for other purposes.

Another object is the effective hydrogenation of ay fatty acid mixturewhich itself contains volatile hydrogenation inhibiting factors byfractionally distilling the mixture to produce one or more fatty acidfractions containing the inhibiting factors and another fraction whichcan be hydrogenated with ease.

An additional object of the invention is the provision of a method forproducing a saturated fatty acid composition of relatively uniformmolecular weight from mixed fatty acids of 55 varying molecular weightand containing unsaturated constituents.

Still another object of the invention is the production of a fatty acidmixture by hydrolyzing a triglyceride, subjecting the fatty acid mixtureto a fractionation procedure in which there is produced an overheadproduct containing low boiling hydrogenation inhibiting factors, abottom product containing high boiling volatile hydrogenation inhibitingfactors, and an intermel diate product, and subsequently subjecting theintermediate product to hydrogenation free of these factors, thehydrogenation procedure preferably being conducted with vigorousagitation at a relatively slow and uniform rate as compared with theinitial possible hydrogenation rate.

These and other objects of the invention will be observed upon aconsideration of the following specification and by reference to theaccompanying drawing, in which the single gure is a somewhatdiagrammatic view of apparatus suitable for carrying out the improvedprocess.

The invention includes the discovery that the diflculties encounteredupon occasions in hydrogenating triglycerides such as vegetable oils,and their fatty acids largely may be overcome by subjecting the materialin fatty acid form to fractional distillation prior to hydrogenation toremove volatile hydrogenation inhibiting substances. It is likely thatthe interference with hydrogenation by vegetable oils and their fattyacids is based upon a poisoning of the catalysts employed in the processby volatile impurities which develop in the oil or fatty acids. Nickelis widely used as a catalyst for hydrogenation processes, since it iseffective and more economical than platinum. Other metals such aschromium also have been suggested as catalysts in the hydrogenationprocess. Where the oil or fatty acids are hydrogenation-resistant, thereaction will proceed but the amount of catalyst required is excessive.y

Where a triglyceride proves to be hydrogenation-resistant it may befreed of the inhibiting factors after conversion into acid form by afractional distillation procedure in which inhibiting factors, which arevolatile, are isolated into one or more fractions such as the overheadfraction and the high boiling fraction. In the case of such an oil afatty acid mixture may be produced as by the well known Twitchellmethod. The splitting operation generally will be effective to hydrolyzeapproximately 96 per cent of the triglycerldes. The particular'nature ofthe fatty acid mixture will depend upon its source. This source may becorn oil, cottonseed oil, soy bean oil, or the like. 'Ihe fatty acidsresulting from hydrolysis of the hydrogenation-resistant vegetable oilmay be hydrogenated effectively if first subjected to fractionaldistillation to eliminate volatile inhibiting factors. 'I'he procedureinvolved in the fractional distillation may be as described in Potts andMcKee Patent 2,054,096.

The fatty acid feed stock is passed through line III into a feed heaterII, this heater preferably being a tube still in which the temperature`of the fatty acid stock is increased suciently to provide forfractional distillation. The heated stock then passes into a fractionaldistillation column indicated at. I2.

Within the fractionating column are positioned a series of superimposedbubble trays I3 having capped vapor vents I3 and liquid down spouts I4.The heated fatty acid stock is flashed into the fractionating column andthere vaporized. The vaporized series of zones of liquid fatty acidshaving de,- creasing boiling points. From the upper of these zonesrepresented by the bubble trays is taken a vaporous overhead productwhich is condensed after passing off through line I5. The requisiteamount cf the condensed overhead product is returned to the upper bubbletray as reflux liquid. The non-volatile or high boiling constituents ofthe fatty acid mixture pass downwardly across the bubble trays in thelower portion of the colunm. Superheated steam is introduced throughline I6 in the bottom of the column and passes upwardly therethroughcountercurrent to the downward flow of liquid fatty acids. understoodthat where the mixture entering the tower is not completely hydrolyzedthe unsplit triglycerides will flow downwardly to the bottom of thetower against the countercurrent of upwardly rising steam. Thus, in thecase of a hydrolyzed oil which has not previously been subjected todistillation, there will be present a small portion of triglycerideswhich are removed as a bottom product through line I1.v

The upwardly rising steam strips volatile products from the downwardlyflowing liquid material, and the resulting mixture of steam and vaporousfatty acids pass upwardly in heat exchange contact with the zones ofliquid fatty acids.

The heat necessary for fractionationvmay be supplied by the feed stockand the superheated steam passing through line I6. The bottom productalso may be heated and recirculated to provide additional heat.

' Intermediate the top and bottom of the fractionating tower is provideda side stripper Il. The stripper I8 takesl liquid fatty acids from anintermediate plate in the tower through line I9, this liquid fractionpassing downwardly through the perforated plates 20 of the stripperagainst an upwardly rising flow of superheated steam introduced throughthe line 2l into the bottom of the stripper. The steam and the lowerboil'- ing fatty acids stripped from the liquid fatty acids flowingthrough the stripper I3 pass back into the tower through the overheadline 22.

The operating conditions of the fractionating procedure Awill dependupon the particular nature of the fatty acid mixture and upon `otherfactors such as the type of product desired. Normally it is preferred tomaintain the fractionation tower under a high vacuum such as may beproduced by a .iet condenser. The fraction or It will be' fatty acidspass upwardly through a fractions in which the volatile hydrogenationlnhibiting factors are isolated by the fractionation procedure willdepend upon such factors as the particular nature of the factors and thetype of product desired to be hydrogenated. In many cases the fatty acidmixture will contain both low boiling and high boiling hydrogenationinhibiting factors. v

Where the hydrogenation inhibiting factors are removed in the overheadproducts or in lthe'bottoms, the fractionated fatty acids removedthrough line 23 are conditioned for hydrogenation. passed into theconventional hydrogenation autoclaveindicated at 24 after being admixedwith a nickel catalyst passed into line 23 through the line 25.

The procedure by which hydrogenation is ef-l fected is quite well known.The catalyst itself may be prepared by reducing nickel formate in thepresence of an oil such as tallow, the ,reduction being effected byheating the mixture to a temperature of about 250 C. The reduced nickelcatalyst is in the form of minute particlesl of active metallic nickeldispersed in the oil vehicle. Other conventional catalysts may beproduced by well known methods.

In the autoclave 24 the mixture of fractionated fatty acids andcatalysts are subjected to agitation in the presence of an atmosphere ofhydrogen introduced fromthe source 26. l

After passing through the hydrogenation autoclave 24 the fatty acids arewithdrawn through the line 21. In some cases it will be founddesirableto employ a series of hydrogenators. That is, the productpassing through line 21 may be then passed through a furtherhydrogenation apparatus to increase the` degree of saturation. Thisrepetition of the hydrogenation process is less necessary in the case ofa. fractionated fatty q fractionated material.

By the combined fractionation and hydrogenation procedures it ispossible to producel special compositions or relatively pure chemicalcompounds. For examplerit is possiblefto treat impure cottenseed fattyacids in accordance with the combined procedure in which an intermediatefraction is .produced consisting'of a mixture of linoleic and oleicacidsand this' mixture is com- Y pleteiy,y hydrogenated to produce relativelypure stearic acid. This product `is to be compared with the ordinarystearic acid of commerce which is a mixture of approximately 60 per centpalmitic acid and 40 per cent stearic acid;

In another example of the process palm voil can be hydrolyzed andtheresulting fatty acid composition subjected to fractionation to produce acompositionV containing percent palmitic acidV and 10 per centunsaturated acids. .The fractionated composition then can vbehydrogenated to convert the unsaturated acids to stearic acid, so thatthe-hydrogenated mixture will contain vabout, 90 per cent palmitic'acidand 10 per cent stearic acid. For all practical pur.-

poses this is equivalent to pure palmitic'acid.

In the manufacture of soap it often is desirable to increase the degreeof saturation of certain of the fatty acid constituents. This conversionof the fatty acids is practical where the acids are initially subjectedto .a fractional distillation pro- These fractionated fatty acids may becedure to eliminate the hydrogenation inhibiting factor of the originalfatty acid mixture.

A desirable soap may be made by subjecting a vblack fatty acid stockcontaining 80 per cent fatty acids and 20 per cent oil to fractionationto produce a special fatty acid composition free from hydrogenationinhibiting factors and a bottom product containing the unsplit oil andunsaponifiable constituents of the original mixture. After hydrogenationthespecial fatty acid composition is ready for saponication. The bottomscontaining 8 to 15 per cent unsaponifiable substances may Ibe split anddistilled to provide avolatile portion and pitch. The volatile portion,which may contain 1 per cent unsaponiable substances, then is subjectedto fractionation to produce an acid fraction and a bottom productcontaining high boiling fatty acids and a relatively large percentage ofunsaponifiable substances. The bottom product may be discarded or usedfor any desired purpose, while the fractionated acids free of thehydrogenation inhibiting factors contained in the bottom product may besubjected to hydrogenation and subsequently used in the production ofsoap or other compounds.

In each of the examples specified the success of the process dependsupon removing the hydrogenation inhibiting factors of the original fattyacid mixture by fractionation prior to the hydrogenation step. Althoughthe undesirable constituents in so far as the hydrogenation procedure isconcerned are volatile, the constituents may be fractionated out of theoriginal mixture.

For the purpose of fractionating out the hydrogenation inhibitingportion of the fatty acid mixture the proper number of bubble trays areprovided in the tower, the exact number being influenced in many casesby the desire for producing a special composition for particularpurposes. In any case there is produced such a separation as willprovide a bottom product, an overhead product which is returned in partas refiux liquid and a fraction which is free from the hydrogenationinhibiting constituents of the original fatty acid mixture.

The factors which inhibit hydrogenation apparently are complex innature. In certain fatty acid mixtures the inhibiting factor will beisolated in the low boiling or overhead fraction. while in otherinstances theinhibiting factors will be found in a high boiling fractionor bottom product. Often both the overhead and bottoms may contain theinhibiting factors while the intermediate fractions will be found freeof the inhibiting factors and easily hydrogenated. The commoncharacteristic of fatty acid mixtures containing hydrogenationinhibiting factors is that they may be divided by fractionaldistillation into a. fraction containing the inhibiting factors and afraction which is free of these factors.

After the fractionation and hydrogenation, the hydrogenated fatty acidsmay be re-esterifed by ordinary methods to produce synthetic mono, di,or triglycerides having special characteristics not possessed by theoriginal triglyceride from which the fatty acid components were derived.Thus, esters of uniform molecular weight may be produced from mixedacids containing both saturated and unsaturated constituents. Glyceridesof a single acid may be produced economically.

It will be recognized that the operating details f the fractionationprocedure, as well as the hydrogenation procedure, may be varied widelywithout departing from the scope or the invention as defined in theappended claims.

We claim:

1. 'lhe process which comprises subjecting a mixture of fatty acidscontaining unsaturated constituents to iractional distillation toproduce a volatile bottom fraction containing a hydrogenationinhibiting. factor, a volatile overhead fraction containing ahydrogenation inhibiting factor, and a volatile intermediate iractloncontaining unsaturated fatty acids. and subjecting the intermediatefraction to hydrogenation.

2. The process of treating a vegetable triglyceride containing anhydrogenation mhibiting factor, which comprises subjecting thetriglyceride to hydrolysis to produce a mixture of fatty acidscontaining said hydrogenation inhibiting factor and unsaturated fattyacids, subjecting said mixture to fractional distillation to produce avolatile overhead fraction containing said lactor and anotherunsaturated fatty acid-containing f'raction, and subjecting saidunsaturated iatty acid-containing fraction to hydrogenation.

3. 'lne process which comprises subjecting a triglyceride containingunsaturated fatty acid constituents and a volatile hydrogenationinhibiting factor to liydroiysis to produce a mixture containing atriglyceride, said hydrogenation innibiting factor and unsaturated fattyacids, subjecting said mixture to fractional distillation to produce abottom fraction containing said triglyceride, volatile high boilingfatty acids, and said hydrogenation inhibiting factor, and a fatty acidfraction containing unsaturated fatty acidsl and subjecting said fattyacid fraction to hydrogenation in the pi'esence of a metallic catalyst.

4. The process which comprises subjecting a triglyceride to hydrolysisto produce a mixture containing triglycerides, a hydrogenationinhibiting factor, and saturated and unsaturated fatty acids,'passingsaid mixture through a continuous heater to raise the temperaturethereof sufciently for distillation of said fatty acids, passing theheated mixture into a vaporization zone, passing the resulting vaporsupwardly through a series of zones of liquid fatty acids havingdecreasing boiling pomts, condensing fatty acid vapors from the upper ofsaid zones, returning at least a portion of the condensed material tothe upper of said zones as reflux liquid, withdrawing a bottom productcontaining said triglycerides and a hydrogenation inhibiting factor,withdrawing an intermediate fraction containing unsaturated fatty acids,withdrawing an overhead fraction containing a hydrogenation inhibitingfactor, and subjecting said unsaturated fatty acids to hydrogenation inthe presence of a nickel catalyst.

5. The process which comprises subjecting a triglyceride to hydrolysisto produce a mixture containing triglyceride, a hydrogenation inhibitingfactor, and saturated and unsaturated fatty acids, subjecting saidmixture to fractional distillation to produce an overhead volatilefraction containing said hydrogenation inhibiting factor and low boilingfatty acids, and another fraction containing the unsaturated fattyacids, said last-mentioned fraction being substantially free of thehydrogenation inhibiting factor, the boiling points of the bulk of thesubstances in said last-mentioned fraction being substantially abovethose of the bulk of the substances in the overhead fraction, andsubjecting the fraction containing the unsaturated fatty acids tohydrogenation in the presence of a. metallic catalyst.

6. The process which comprises subjecting a triglyceride to hydrolysisto produce a mixture containing triglyceride, hydrogenation inhibitingfactors, and saturated and unsaturated fatty acids, subjecting saidmixture to fractional distillation to produce an overhead volatilefraction containing one of said hydrogenation inhibiting factors and lowboiling fatty acids, an intermediate volatile fraction containing theunsaturated fatty acids and being substantially free of hydrogenationinhibiting factors, the boiling points of the bulk of the substances inthe intermediate fraction being substantially above those in theoverhead fraction, and a volatile bottom fraction containing one of saidhydrogenation inhibiting factors and high boiling fatty acids, theboiling points of the bulk of the substances in `said bottom fractionbeing substantially above the boiling points of the bulk ofthesubstances in the intermediate fraction, and subjecting saidintermediate fraction `to hydrogenation in the presence of a metalliccatalyst.

7. The process of treating a fatty acid mixture derived from atriglyceride oil and containing unsaturated fatty acids andhydrogenation inhibiting factors which comprises subjecting said fattyacid mixture to fractional distillation to produce an upper volatilefraction containing one of said hydrogenation inhibiting factors and alower volatile fraction containing another of said hydrogenationinhibiting factors and an intermediate volatile fraction containingunsaturated fatty acids and being substantiallyfree ofsaid hydrogenationinhibiting factors, and subjecting said intermediate volatile fractionto hydrogenation. Y

8. The process of treating a mixture of fatty acids derived from atriglyceride oil'and containing unsaturated fatty acids and hydrogenaftion inhibiting factors, `which comprises subjecting said mixture offatty acids to fractional distillation to produce an upper volatilefraction which contains one` of said hydrogenationeinhibitingfactorsand` a lower volatile fraction which contains another of saidhydrogenation inhibiting factors and `an intermediate volatile fractioncontaining unsaturated acids and being substantially free of saidhydrogenation inhibit,- ing factors, the boiling points'of the bulk ofthe substances in each of the said fractions being substantiallydifferent, and subjecting -said intermediate volatile fraction tohydrogenation Vto produce a synthetic composition of relatively uniformmolecular weight.

9. A process as called forin claim 'l in which said mixture is derivedfrom cottonseed oil. L y

10. A process as called for in claim 7 in which said mixture is derivedfrom soy bean oil.

, 11. A process as called for in claim '1 in which said lower volatilefraction is contained along with glycerides in a bottoms product.V

JOHN E. MCKEE. ORLANDO GRAZIANI.

